Update 3pm: A father found strangled in his flat alongside his daughter was a convicted sex offender.
Detectives investigating the deaths of Noel Brown, 69, and Marie Brown, 41, also believe it is a "strong possibility" she disturbed the attackers as they attempted to dismember his body, Scotland Yard said.
Mr Brown and his only daughter were found strangled at his flat in New Butt Lane, Deptford, south-east London, at about 2.45am on Monday after police responded to a welfare concern.
Police are trying to establish why they were killed but Detective Superintendent Paul Monk said Mr Brown's conviction in 1999 for a sex offence, for which he served four years in prison, was not "screaming out" as a motive.
He said "nothing" had happened in Mr Brown's life in the 18 years since the conviction to suggest that was the reason for the murder.
Mr Monk said: "The offence was a sex offence, he was convicted and served time and was released in 2004 but I'm not prepared to give any more details."
Earlier: A father murdered along with his daughter were both found strangled in a London flat with no signs of forced entry, UK police said.
Noel Brown, 69, and Marie Brown, 41, were found dead at his home in New Butt Lane, Deptford, at about 2.45am on Monday.
Metropolitan Police detectives said they have found no evidence that Mr Brown was killed because of a large gambling win, although he had visited his local betting shop Paddy Power on the day he was last seen alive.
A neighbour saw Mr Brown at his home at around 8pm on Thursday November 30, and days later at around midday on Saturday December 2, his daughter went to his flat out of concern for his welfare - she was not seen alive again.
After forensic searches of the area and gathering hours of CCTV, police have appealed for the public’s help and urged two men who visited Mr Brown’s flat in the days before he was found dead to come forward.
Detective Superintendent Paul Monk said: "At this early stage we are keeping an open mind regarding the motive. However, it was clear to the responding officers that there were no signs of forced entry to the property.
"One of our key lines of inquiry is to establish if the suspect or suspects were known to Noel and if Marie disturbed them.
"One of the key strands of our investigation is understanding all we can about Noel’s life. He was well known and liked locally.
"We know that Noel used to go to his local betting shop, Paddy Power, in Deptford High Street and had in fact been there during the day he was last seen alive on 30 November.
"There has been speculation that his murder was as a result of a large gambling win. However, at this time there is no evidence to suggest this was the case.
"I am keen to hear from anyone who saw Noel in the days leading up to his death or saw anyone or anything unusual in or around New Butt Lane, SE8 during that time.
"This is a deeply distressing time for Noel and Marie’s family as they come to terms with their loss."
Mr Monk said officers did not believe the motive was burglary or robbery and said there may be more than one suspect.
He said: "One of the possibilities I’m investigating is that these people were known to Noel so I’m particularly keen to hear from anybody that knew Noel, knew his lifestyle and knew people he may associate with.
"There were no signs of a disturbance so I don’t think it’s a burglary or robbery or anything of that nature. There were no signs of forced entry and I think Marie probably went to the address on the Saturday and may have disturbed his attacker or attackers - it may be one it may be many more."
Although Mr Brown was a regular gambler, placing "very small bets" every day at the betting shop, Mr Monk said his biggest win was thought to be up to £15 or £20.